In view of the problem that the instantaneous impact pressure increases when the piston pump wet spraying machine changes direction,which seriously affectes the hydraulic system,the simulation model of S-tube valve reversing system was established by using AMESim platform;the influences of different proportional valve reversing frequency,oil bulk modulus and hydraulic pump displacement on the impact of S-tube valve system were studied.The results show that as the frequency increases,the reversal time of the proportional valve can be shortened,the system tends to be unstable,and the return peak impact force is increased,therefore,a low frequency should be selected to increase the commutation time and reduce the impact force in the project;during the operation of the wet spraying machine,hydraulic oil with a small bulk modulus has small oscillation and impact force,so the system tends to be stable;when the displacement of the constant power variable pump is increased,the peak impact force of the system decreases at the start and the peak impact force increases on the return stroke,so appropriately reducing the displacement can reduce the impact force brought by the proportional valve reversing.